Automatic telecommunication systems



Feb. 10, 1959 K. A. ANULF 2,

AUTOMATIC TELECOMMUNICATION SYSTEMS Filed Aug. 12, 1955 2 Sheets-Sheet 1ATTORNEYS Feb. 10, 1959 K. A. ANULF v 2,873,323-

AUTOMATIC TELECOMMUNICATION SYSTEMS b I I I Ab lRFV i/erw INVENTORATTORNEZS 2,873,323 AUTOMATIC 'I'ELE'COMMUNICATION SYSTEMJ Karl ArneAnulf, Nasbypark, Sweden Application August 12, 1955, Serial No. 528,022

Claims priority, application Sweden August 13, 1954 7 Claims. (Cl.1'79-175.2)

The present invention has regard to an arrangement in automatictelecommunication systems comprising selectors forestablishingconnections and controlling members arranged to cause the setting ofengaged selectors in dependence of incoming switching signals by meansof controlling signals controlling the selectors, which are providedwith means for returning to the controlling members a return signal as acriterion on the operation of the respective selector in dependence of acontrolling signal.

Such systems, such as telephone and telegraph offices, were previouslysupervised continuously by human personnel checking during all the 24hours the safe opera tion of the switching equipment.

As the modern telecommunication systems are materially more reliable inoperation than older systems it has been possible to reduce the humansupervision to a substantial extent, and a great number of exchanges andofi'ices are not supervised at all and the remaining exchanges are onlysupervised during a part of the day.

, Due to the fact that the human supervision is reduced to a minimumthere is a need for means for automatically identifying defectiveswitching courses and blocking defective switching members andconnections. Relatively simple faults may sometimes cause greatobstacles for the trafiic, and at least during reduced trafiic, evencompletely block ditier'ent tratfic routes.

. A fault in a connection usually shows the same characteristics as ifan overloading of the traffic route were a present, in that the call cannot be switched forward. Hitherto it has been an unsolved problem tomake a distinction between these two kinds of disturbances. In the past,attempts have been made to solvethe problems by recording thoseswitching trials, which have not been completed immediately and to finddefective switching members by statistic analysis of the extensivematerial obtained. The faults which may be detected in this way will ofcourse remain and cause traffic disturbances for an extended period oftime until they are found. It is an object of this invention to providea simple arrangement, by means of which switching courses in whichfaults occur can be identified and distinguished from such switchingcourses that cannot be completed due to the occurence of denied calls..The establishment of a connection takes place in a predeterminedsequence, and the various phases of the calls in the modern systems arecontrolled by controlling members operating the switching members. Whenan operation has been completed, a return signal, usually termed receiptsignal, gives an indication that the operation has been duly concludedbefore the next operation is started. In the case of a fault this returnsignal will fail to be received while in the case of a denied call thereturn signal will be received after some time. This time, however, maybe so long that the call has been abandoned and concluded before thecondition of denied call is broken oif. l 1

i The arrangement according to the present invention is contact bank ofa .line finder S.

7 2 characterized by the fact that it comprises means for effecting independence of an incoming switching signal a holding of engagedselecting means independently of the maintenance of the switchingcondition initiating the switching course and for releasing this holdingin dependence of a corresponding return signal, and that it furthercomprises a time measuring device for measuring the space of time of theholding condition and efiecting a fault indication at the occurrence ofsuch a space of time that considerably exceeds the likely average delayfor denied calls.

Due to the fact that the operation time of the time measuring device isso chosen that it substantially exceeds the normal or average delay fordenied calls, a denied call can be distinguished from a fault withalmost complete certainty, since a denied call would have-been brokenoflf before the operation of the time measuring device.

If there is an average delay of 15 seconds for denied calls only 6X10-of the calls will still remain after ten minutes at a normaldistribution of the delays.

If a fault indication takes place after this time and it is assumed thatthe percentage of faulty connections is 0.04% only one indication of 610 will be caused by denied calls, which number is quite negligible.

An embodiment of the invention will be more closely described inconnection with Figures 1 and 2 on the drawings, which are to be placedwith Fig. l on the top of Fig. 2. The invention is here applied to aregistercontrolled telephone system, in which the selectors arecontrolled by impulses from a register containing in a known manner thecontrolling members for the selectors. Ab designates a callingsubscriber's set connected in usual manner together with othersubscribers sets to the IGV, IIGV and LV designate selector stages, thatis first group selector, second group selector and final selectorrespectively, which are arranged in a well known manner. A register isdesignated REG, and RFV is a connecting member for the register such asa register-preselector. in. the selector stages controlled by theregister the aforesaid return signal consists of the connection of minuspotential to the b-conductor, which signal is momentarily transmittedfrom the succeeding selecting member in connection with the connectionthrough a selecting stage.

A call from the subscriber Ab is connected through the line finder S inthe usual manner, .so thatthe connecting relay S1 is operated. A freeregister REG is hunted out and connected in a known manner by theoperation of relay RFVl in the register-preselector. (The operationcircuits of relays S1 and RFVl are not shown on the drawing.)

When the register REG has been connected, the im pulse relay R1 isoperated by current from plus through the upper winding of relay R1,contacts RFV1-3 and 81-2, the b-conductor of the subscriber Ab, throughthe telephone set Ab, the a-conductor, contacts 51-1 and RFVl-S andthrough the lower winding of relay R1 to minus. Theslow-releasingholding relay R2 is thereby operated by current through contact Rl-l.

The. operation of relay R2 has as a result that (1) this relay takesover the holding from the register of the register-preselector by a pluspotential connected through contact R2-1 and (2) that a holding circuitfor relay S1 in the line finder Sis formed from plus through contactR2-2, contacts RFVl-l and 81-3 and through the winding of relay S1 tominus, whereby the subscriber is kept connected to the line finder S. 7

I The digits dialled by the subscriber Ab are now stor in a known mannerin the register REG. Under the cooperation of. a selector V0 the firstdigit is registered.

by the selector V1, the second'digit by selector V2 eta;

, Fatented Feb. 1%, 1959;

9 Then the operation of the selectors is started. When the first digithas been dialled a circuit is closed from contact Vii-1 through brakecontact R4-3, through the winding of the impulse transmitting Iclay R5to an impulse generator 16.

Relay R5 now starts to alternately operate and release in time to theimpulses from the impulse generator, whereby the selector IGV and thecounting member V are operated stepwise in synchronism. The selector IGVis operated in the following way: relay G11 in selector IGV obtainscurrent impulses from minus at contact RS-l, through contact RFV1-6,through the winding of relay G11 and through contact G14-3to plus.Hereby the selector magnet G13 will operate in time to the impulsessupplied by contact Gil-1. The selector V10 is operated by impulsestransmitted by contact RSEZ.

'When selector V10 has reached the position corresponding to the digitsregistered b'y'the selector V1 the controlling relay R4 operatesbycurrent from plus at contact R476 through field contact 1 in theselcctorV11, a field contact in selector V1 corresponding to the registereddigit, a corresponding field contact in selector V10 through the windingof relay R4..to minus. Relay R4 obtains holding current through its.Contact. 34-2 and through contact R3-.-1 on relay R3.

Relay R4 breaks the impulse circuit for relay R5 at contact R4-3,whereby. the operation of selector IGV, which now has been set on thedesired decade, is stopped.

Furthermore impulses are connected through contact Rat-.1 to a timemeasuring device T, arranged to operate at two different times, oneafter ten seconds andthe other after 10 minutes for example.

The first mentioned time is so calculated as to be less than the likelyaverage delay for denied calls but yet exceeds the normal switchingtime, while. the, other time considerably exceeds said, average delay.The selector V11, which successively connectsthe translating circuitsfor the difierent switching stages is advanced by current through makecontact R4-4. The counting member V10 is restored by contact R4-5, andthe translating circuit is opened by contact R4-6. The register nowwaits in this position for the return signal.

The selector IGV, the numerical setting ofnwhich was concluded when theimpulse sending was finished in the register, has in the meantimestarted the, hunting, for a.

freeline to the selector IIGV. When sucha line is seized; relay G14 inselector IGV is operated and connects the speech conductors a and 11.Also, relay G22 in selector IIGV, is operated in series, wi h. relayG14.v However,

relay G22 is slow-operating and duringrthc delay a. return sualis s o eis hich r tu n s gnal consists of the connection of minus potential totheb-conductor. through break contact (322-1. Thesignalis received. byrelay R3, which is operated. Hereby the break contact R3-1 is opened andrelay R4 releases.

On the operation ofrelay R4 thetime measuring device T is restored bythe opening of contact .R4-1, andthe next switching stage can beoperated.

It there had been a denied call in selector IG,V and the delay hadexceeded 10 seconds the time mcasuringdevice.

S1- releases and is de-energized' and releases the calling subscriberfrom the line finder.

When the condition of'denied callceases, a return signal is received andrelay R4 releasesin a manner described above, Hereby the timemeasuringdevice Tis restored,

relay R6 releases, the register-preselector REV loses.

cl. its holding current and all the engaged bars are released.

It may now be assumedthat the establishment of the connection has beencompleted in a normal Way through the selector IGV and that accordinglythe setting of selector IIGV for connecting the final selector LV has totake place. Further it may be assumed that the selector IIGV is faultydue to a rupture in the controlling circuit of the operating magnet ofthe selector, which rupture is indicated by a cross on the drawing.

The relay R5 in the register transmits impulses in the same way as onthe setting of the group selector IGV, which impulses are received byrelay G1 in group selector IIGV. When the impulse sending is concluded,relay R4 is operated in the manner described above, so that the timemeasuring device T is energized again. Due to the fault the selector isnot operated, and accordingly no return signal can be transmitted. When10 seconds have lapsed the switching course is locked in: dependently ofwhether the call has been concluded or not, and after 10 minutes thetime measuring device operates fault indicating relay R7 throughcontactT-Z. This relay lights the fault indicating lamp F1 belonging to theregister and transmits through contact R7-4 a fault indicating signal tosupervising personnel on the same or another ofiice. RelayR7 besideswarrants the holding of relay R4 and switching mentcontact R72, so thatthe switching condition at the instant of fault indication cannot beunduly changed.

The fault indication remains until the restoring switch AK is operated,and during this time the faulty switching member is automaticallyblocked. In the same way as previously described the calling subscriberis released when the call ceases, that is when the micro-telephone isreplaced. By studying the position of the selector V11 the fault can beeasily located, so that either the required reparation can be carriedout immediately or, if the fault is more serious, the faulty switchingmember can be taken out of trafiic in the usual way.

In the embodiment described above the time measuring, device is arrangedto operate at two different points of time, that is first after ashorter. time for effecting a holding of the engaged switching membersand then, after a longer time, for causing a fault indication. This isadvantageous with regard to the fact that a calling subscriberfrequently does not wait at a denied calli until the condition of deniedcall ceases but concludes. the call before. then, e. g. after 20'seconds. Although it is possible within the scopefof. the general ideaofthe vention to have. the time measuring device operate only" with thelonger time and to allow the holding'to take place with no delay,thisvwill, however, involve the disadvantage" that switching membersengaged for a connection, in which a denied call condition is occurring,will'be' kept eugaged until this condition ceases on the interruption ofthe call before the cessation of the denied call condition, and thiswill of course reduce the possibilities to obtain connection through thesystem. The first operatingtime' of the time measuring device. shouldaccordingly be so chosen thatit exceeds the normal time for'establishinga connection but is less than the time, for which itmay;

be assumed that a subscribernormally'waits fora" speechconnection.Inevery case this time should'be materially shorter than the timemeasured for the fault indication. On the other side it is possible to'equip only a small number of controlling members, e. g. only oneregister, with a time measuring device and arrangements for hold? ingand releasing engaged selectingmembersinsystems; where a plurality ofcontrolling members are alternately accessiblev for the establishment ofconnections, for in= stance the controllingvmembers': are situated inalter nately connectable registers. These. controlling mam bers or this.register. respectively will then" act as" a tests ing device, which willmake a teston theditf'e'rent con nectionssuccessively as they areconnected to" it: Iii such a case an extended occupation of thcswitchingmem= assess-s invention will thereby be common for all the succeedingswitching stages. In systems having separate controlling members foreach selecting stage ,or having several registers along the route thedifferent sets of controlling members or the diflerent registers may ofcourse be provided with individual arrangements accordingto the,invention. It will then also be possible to release all the precedingswitching stages on the occurrence of a fault according to the principledescribed above for releasing the line finder and the calling subscriberin the shown embodiment.

A further feature of the described embodiment is that the return signalsarrive when the selector setting in the respective switching stage hasbeen concluded and thus act as signals indicating that the register maycontinue the signal sending for setting the next succeeding switchingstage. The invention is, however, as well applicable to systems in whichthe selectors transmit return signals during their setting consisting ofso-called back impulses. In such systems the failure of back impulseswill cause fault indication in a way, which in point of principle is thesame as in the described embodiment. The time measuring device is thensuitably started by starting rclays or the like which are operated forthe transmission of an operating signal to the selector.

Particularly in non-supervised offices and exchanges it may beadvantageous not to obtain durable holding of faulty connections at eachoccurrence of a fault but instead to arrange the time measuring deviceto advance a counting member for each operation, which counting memberafter having registered the occurrence of a fault releases theconnection by automatically operating a contact corresponding to therelease contact AK. The counting member can easily be arranged in such away, that it transmits a fault signal to a superior otlice after apredetermined number of fault indications and simultaneously fails torelease the connection, whereby a mender can identify the faultyconnection at an inspection.

I claim:

1. In a telecommunication system, selectors for establishing connectionsbetween calling and called circuits,

control means for operating said selectors, means for connecting saidcontrol means to one of said circuits in response to calling conditionon said one circuit, means in said selectors for sending return signalsto said control means in case of proper function of the selectors,holding means for holding engaged selectors in engaged conditionirrespective of the continuance of the calling condition on said onecircuit, means for releasing said holding means in response to saidreturn signals, timing means for measuring the duration of the operatedcondition of said holding means, and indicating means operable by saidtiming means in the case that said duration exceeds a predeterminedtime.

2. In a telecommunication system, selectors for establishing connectionsbetween calling and called circuits control means for operating saidselectors, means for connecting said control means to said circuits inresponse to calling condition on said circuits, means in said selectorsfor sending return signals to said control means in case of properfunction of the selectors, holding means for holding engaged selectorsin engaged condition 1rrespective of the continuance of the callingcondition on said circuits, means for releasing said holding means in,response to said return signals, timing, means for measuring theduration of the operated conditionoi said holding means, indicatingmeans operable by said timing means in the case that said durationexceeds a predetermined time, and means operable by said timing ievice-concomitantly with operation of said indicating means torenderineiiective said means for releasing the holding means in response toreturn signals.

3. In a telecommunication system, selectors for establishing connectionsbetween calling and called circuits,

control means for receiving switching signals and sending controlsignals to said selectors for setting said selectors in accordance withthe switching signals, means for connecting said control means to one ofsaid circuits in response to calling condition on said one circuit,means in said selectors for sending return signals to said control meansin case of proper operation of the selectors, holding means responsiveto the transmission of said control signals for holding engagedselectors in engaged condition irrespective of the continuance of thecalling condition on said circuit, means responsive to said returnsignals to release said holding means, timing means for measuring theduration of the operated condition of said holding means, and indicatingmeans operable by said timing means in the case that said durationexceeds a predetermined time.

4. In a telecommunication system, selectors for establishing connectionsbetween calling and called circuits, control means for receivingswitching signals and for sending control signals to said selectors forsetting said selectors in accordance with the switching signals, meansfor connecting said control means to one of said circuits in case ofcalling condition on said one circuit, means in said selectors forsending return signals to said control means in case of proper functionof the selectors, timing means, means for starting the operation of saidtiming means in response to the transmission of said control signalsfrom the control means, holding means operable by said timing meansafter a first predetermined interval to hold engaged selectors inengaged condition irrespective of the continuance of the callingcondition on said circuit, means responsive to said return signals torelease said holding means if operated and to reset said timing means,and indicating means operable by said timing means after a secondpredetermined interval longer than said first predetermined interval.

5. In a telecommunication system including calling and called lines,selectors for establishing connections between said calling and calledlines, a plurality of control means for controlling operation of saidselectors, means for connecting any one of said control means to one ofsaid lines in response to calling condition on said line, means in saidselectors for sending return signals to said control means in case ofproper operation of the selectors, at least one of said control meanscomprising in combination: holding means for holding engaged selectorsin engaged condition irrespective of the continuance of the callingcondition on said one line, means responsive to said return signals torelease said holding means, timing means for measuring the duration ofthe operated condition of said holding means, and indicating meansoperable by said timing means if said duration exceeds a predeterminedtime.

6. In a telecommunication system including calling and called lines,selectors for establishing connections between said calling and calledlines, registers for controlling operation of the'selectors, connectingmeans operative in response to the initiation of a call on one of saidlines serving as a calling line to seize a register and to connectselectors to the seized register, relay means under control of the saidcalling line and responsive to the seizure of a register to establish afirst holding circuit for said connecting means, means in said selectorsfor sending return signals to the said. seized register in case ofproper function of the selectors, means in said ,for said connectingmeans, said second holding circuit being independent of the firstholding circuit, means responsive to' said return signals to releasesaid means for establishing a second holding circuit, timing means formeasuring the duration of the operated condition of said means forestablishing a second holding circuit, and indicating means operable bysaid timing means if said duration exceeds a predetermined interval. 7

i 7. In a telecommunication system, selectors for establishing'connections between calling and called circuits, control means foroperating said selectors, means responsivc to the initiation of a callfrom one of said circuits to connect said control means to said onecircuit, means in said selectors for sending return signals to saidcontrol means in case of proper function of the selectors, holding meansfor holding engaged selectors in engaged jcondition irrespective of thecontinuance of the calling condition on said one circuit, meansresponsive to saidreturn signals to release said holding means, timingmeans for measuring the duration of theoperated condition of saidholding means, indicating means operable by said timing, means if saidduration exceeds a predetermined interval, and means responsive to thecessation of the calling condition on said one circuit to disconnectsaid one'circuit from said selectors and control meansirrespective ofWhether said holding means is in operated condition.

References Cited in the file of this patent UNITED STATES PATENTS2,508,052 Williford May 16, 1950 2,513,049 Powell June 27, 19502,542;800 Dehn et a1 Feb. 20, 1951 2,635,148 Shepherd Apr. 14,19532,657,271 Henry Oct. 27, 1953

